Well sects arise out of differences, and the messenger of Allah peace be upon him told us that Islam will split into 73 sects and only one will go to jannah, the correct one he said is the sect that follow's his sunnah and is upon what him and his companions are upon.
So as long as you make sure that everything you do was done by the messenger of Allah peace be upon him and his companions you'll be ok
some of the differences that the sects have are, shia's curse the prophets companions among many other viole things and sunni's don't do this, instead they follow the example of the companions aswell as the prophet peace be upon him.
And another difference is with the sufi's, they have alot of innovated stuff like congregational dhkir, this wasn't done by the prophet (peace be upon him) or his companions. They never sat in a room with the lights off in the dark going, "Allah hu" as far as I'm aware.
Also Sufi's tend to refer to themselves as "Sunni's" and call every 1 else who doesn't believe in sufism a "Wahaaabi" which isn't right because what they refer to as wahaaabi's are people who are the real sunni's because they're trying to follow the sunnah as much as possible.
I classify myself as a sunni because I believe you should follow the prophet's sunnah as much as possible and reject everything that wasn't done by him or his companions. But this doesn't seem to register with other sects.